Oil cooling and filtering system of automatic transmission

ABSTRACT

An oil cooling and filtering system of a transmission is described which comprises first and second oil passages formed in a given portion of a housing of the transmission. The given portion has an outer surface exposed to the outside of the housing. The first oil passage is fed with a compressed lubricating oil from an oil compressing means and the second oil passage is led to moving parts of the transmission which are to be lubricated. An oil cooler is connected to the outer surface of the given portion. The oil cooler includes a water flow passage and an oil flow passage which are isolated from each other. The oil flow passage has an inlet opening connected to the first oil passage and an outlet opening connected to the second oil passage. An oil filter is installed in at least one one of the first and second oil passages for filtering the lubricating oil flowing in the oil passage. With this arrangement, the oil cooler can be compact in size and simple in construction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to oil cooling and filtering systems of an automatic transmission and more particularly to the oil cooling and filtering systems of a type that is compact in size and simple in construction.

2. Description of the Related Art

In automatic transmissions for wheeled motor vehicles, there is usually employed an oil cooling and filtering system which cools and filters the lubricating oil that flows in the transmission to lubricate moving parts of the transmission to reduce or minimize friction of the same.

FIG. 11 of the accompanying drawings is a conceptual view of a known oil cooling and filtering system of the automatic transmission, which is disclosed in Japanese Laid-open Patent Application (Tokkai) 2003-106419. An oil pump 1, a control valve 2 and moving parts 3 such as gear trains, multiple disc brakes, belt (in case of continuously variable transmission), etc., are all installed in a housing of the transmission. At an outside of the transmission housing, an oil cooler 4 is fixed to a mounting portion 9 of the transmission housing, as shown. The oil pump 1, control valve 2, oil cooler 4 and the moving parts 3 are connected through oil passages 5, 6, 7 and 8. That is, the oil passage 5 conveys the lubricating oil compressed by the oil pump 1 to the control valve 2, the oil passage 6 conveys the lubricating oil adjusted in pressure by the control valve 2 to the oil cooler 4, the oil passage 7 conveys the lubricating oil cooled by the oil cooler 4 to the moving parts 3 which are to be lubricated, and the oil passage 8 conveys the lubricating oil from the moving parts 3 to the oil pump 1. The oil cooler 4 shown in the published application is of a water cooled detachable type. That is, the oil cooler 4 is connected to the mounting portion 9 by means of bolts (not shown) and has a heat exchanging unit 4 b and water inlet and outlet pipes 4 a and 4 c. Cooling water (or cooled water) from a radiator (not shown) is led into the oil cooler 4 through the water inlet pipe 4 a to flow around the heat exchanging unit 4 b to cool the lubricating oil that flows in the heat exchanging unit 4 b, and water thus warmed by the heat exchanging unit 4 b is returned back to the radiator through the water outlet pipe 4 c. Although not shown in the drawing, an oil filter is installed in the heat exchanging unit 4 b of the oil cooler 4 for filtering the lubricating oil. Because the lubricating oil is cooled and filtered under operation of the transmission, the lubricating oil can keep its lubrication effect at a satisfied level thereby optimally lubricating the moving parts 3 of the transmission. That is, due to such oil cooling and filtering system, smoothed operation of the moving parts 3 and suppression of heat generation of the moving parts 3 are achieved at the same time. Under operation of the transmission, the oil filter traps particles of dirt, carbon and metal powder, that would contaminate the lubricating oil, and thus, not only the smoothed operation of the moving parts 3 is promoted but also a smoothed operation of the oil pump 1 and control valve 2 is achieved.

SUMMARY OF THE INVENTION

However, hitherto, the arrangement of the oil filter for such oil cooling and filtering system has been given little thought. In fact, in the system of the above-mentioned published application, the oil filter is simply installed in the oil cooler 4 without deep deliberation, and thus the oil cooler 4 is compelled to have a bulky and complicated construction, which is undesirable when considering a limited space of the engine room of the motor vehicles in which various parts have to be installed.

It is therefore an object of the present invention to provide an oil cooling and filtering system of an automatic transmission, which is free of the above-mentioned drawback.

It is another object of the present invention to provide an oil cooling and filtering system of an automatic transmission, that comprises a compact oil cooler that is detachably connected to an outer wall of a housing of the transmission.

In accordance with a first aspect of the present invention, there is provided an oil cooling and filtering system of a transmission, which comprises first and second oil passages formed in a given portion of a housing of the transmission, the given portion having an outer surface exposed to the outside of the housing, the first oil passage being fed with a compressed lubricating oil from an oil compressing means and the second oil passage being led to moving parts of the transmission which are to be lubricated; an oil cooler connected to the outer surface of the given portion, the oil cooler including a water flow passage and an oil flow passage which are isolated from each other, the oil flow passage having an inlet opening connected to the first oil passage and an outlet opening connected to the second oil passage; and an oil filter installed in at least one of the first and second oil passages for filtering the lubricating oil flowing in the oil passage.

In accordance with a second aspect of the present invention, there is provided an oil cooling and filtering system of an automatic transmission which comprises first and second oil passages formed in a given portion of a housing of the transmission, the given portion having a flat outer surface exposed to the outside of the housing, the first oil passage terminating at the flat outer surface and fed with a compressed lubricating oil from an oil pump, the second oil passage terminating at the flat outer surface and being led to moving parts of the transmission which are to be lubricated; an oil cooler detachably connected to the flat outer surface of the given portion, the oil cooler including a water flow passage and an oil flow passage which are isolated from each other, the oil flow passage having an inlet opening connected to the first oil passage and an outlet opening connected to the second oil passage; a cylindrical bore formed in the given portion of the housing and merged with the first oil passage, the cylindrical bore terminating at the flat outer surface of the given portion; and a cylindrical oil filter installed in the cylindrical bore of the given portion for filtering the lubricating oil flowing in the first oil passage toward the oil cooler.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a conceptual view of an oil cooling and filtering system of the present invention, which is incorporated with an automatic transmission;

FIG. 2 is a partially sectional side view of a portion of the transmission where an oil cooler and an oil filter that constitute an essential part of the oil cooling and filtering system of the present invention are arranged;

FIG. 3 is a sectional view of the oil cooler taken along the line III-III of FIG. 2;

FIG. 4 is an enlarged sectional view of the oil cooler taken along the line IV-IV of FIG. 3;

FIG. 5 is an enlarged sectional view of the oil cooler taken along the line V-V of FIG. 3;

FIG. 6 is a perspective view a depressed element plate that is a part of the oil cooler;

FIG. 7 is a sectional view of a portion of the depressed element plate where a collared opening is located;

FIG. 8 is a sectional view of another portion of the depressed element plate where a simple opening is located;

FIG. 9 is a sectional view of two depressed element plates that are stacked together;

FIG. 10 is an exploded perspective view of the oil cooler, showing a plurality of (nine) depressed element plates which are to be stacked together; and

FIG. 11 is a view similar to FIG. 1, but showing a known oil cooling and filtering system of an automatic transmission.

DETAILED DESCRIPTION OF THE INVENTION

In the following, the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, there is shown a conceptual view of an oil cooling and filtering system of an automatic transmission, which is an embodiment of the present invention.

Within a housing 22 of the transmission, there are installed an oil pump 11, a control valve 12 and moving parts 13 such as gear trains, multiple disc brakes, belt (in case of continuously variable transmission (CVT)), etc.,.

At an outside of the transmission housing 22, there is arranged an oil cooler 14 that is detachably connected to a mounting portion 19 of the transmission housing 22.

The oil pump 11, the control valve 12, the oil cooler 4 and the moving parts 13 are connected through oil passages 15, 16, 17 and 18.

Like in the above-mentioned known system, the oil passage 11 conveys a lubricating oil compressed by the oil pump 11 to the control valve 12, the oil passage 16 conveys the lubricating oil adjusted in pressure by the control valve 12 to the oil cooler 14, the oil passage 17 conveys the lubricating oil cooled by the oil cooler 14 to the moving parts 13 which are to be lubricated, the oil passage 18 conveys the lubricating oil from the moving parts 13 to the oil pump 11.

The oil cooler 14 is of a water cooled detachable type. That is, the oil cooler 14 is detachably connected to the mounting portion 19 by means of bolts (not shown) and has water inlet and outlet pipes 14 a and 14 c connected thereto.

As will be described in detail hereinafter, cooled (or cooling) water from a radiator (not shown) is led into a water flow passage 34 of the oil cooler 14 through the water inlet pipe 14 a, and flows in the water flow passage 34 to cool the lubricating oil that flows in an oil flow passage 33 of the oil cooler 14, and water thus warmed by the lubricating oil is returned back to the radiator through the water outlet pipe 14 c.

As is seen from the drawing, in accordance with the present invention, an oil filter 20 is detachably received in a bore 21 that is formed in a wall of the transmission housing 22. That is, the bore 21 is merged with a downstream end of the oil passage 16. Thus, the lubricating oil from the control valve 12 is filtered by the oil filter 20 before being led into the oil flow passage 33 of the oil cooler 14.

In the following, the detail of the mounting portion 19 of the transmission housing 22 where both the oil cooler 14 and the oil filter 20 are arranged will be described with reference to FIG. 2.

As is understood from FIG. 2, the mounting portion 19 has a substantially flat outer surface to which the oil cooler 14 is intimately and detachably connected in such a manner as will be described in the following.

The mounting portion 19 is formed with a larger bore 23 (that corresponds to the bore 21 in FIG. 1) and a smaller bore 24, which both extend to the flat outer surface of the mounting portion 19. That is, both the larger and smaller bores 23 and 24 are exposed to the outside of the mounting portion 19. As shown, the larger bore 23 is cylindrical in shape and connected to the oil passage 16 formed in the transmission housing 22, and the smaller bore 24 is connected to the oil passage 17 also formed in the transmission housing 22.

Within the larger bore 23, there is neatly installed the oil filter 20. The oil filter 20 comprises a cylindrical housing 20 a and a filter element 20 b put in the housing 20 a. For stably receiving the oil filter 20 in the larger bore 23, the larger bore 23 is formed with a filter seat portion 22 a.

In the illustrated embodiment, the diameter of the larger bore 23 is somewhat larger than the diameter of the oil filter 20 thereby to form a cylindrical clearance (no numeral) therebetween. As shown, in use, a seal member (O-ring or the like) 25 is operatively put between the filter seat portion 22 a and the oil filter 20.

Referring to FIGS. 4 and 5, there is shown in a sectional manner the detail of the construction of the oil cooler 14.

The oil cooler 14 comprises a circular depressed base plate 27, a circular cover plate 26 and a plurality of circular depressed element plates 28 which are the same in shape and stacked together between the base plate 27 and the cover plate 26. In the illustrated embodiment, nine element plates 28 are used.

The base plate 27, the cover plate 26 and the element plates 28 are stacked together in a manner to constitute two, that is, water and oil flow passages 34 and 33 each including a plurality of thin passages R2, R4, R6, R8 and R10 (or R1, R3, R5, R7 and R9). For the reasons as will be described hereinafter, the thin passages R2, R4, R6, R8 and R10 of the water flow passage 34 and the thin passages R1, R3, R5, R7 and R9 of the oil flow passage 33 are alternately arranged to obtain an effective heat exchanging between the cooling water flowing in the water flow passage 34 and the lubricating oil flowing in the oil flow passage 33.

As is seen from FIG. 4, the water inlet pipe 14 a and water outlet pipe 14 b are connected to inlet and outlet openings 26 a and 26 b of the water flow passage 34, that are defined by the cover plate 26.

As is understood from FIGS. 5 and 2, upon mounting of the oil cooler 14 onto the mounting portion 19 of the transmission housing 22, an interior 27 c of the base plate 27 that is merged with the oil flow passage 33 faces the perforated flat outer surface of the mounting portion 19 to which the larger and smaller bores 23 and 24 are exposed.

It is to be noted that under this mounted condition, the oil filter 20 is stably set in the larger bore 23 having an inlet side thereof mated with the oil passage 16 and an outlet side thereof mated with an inlet opening 27 a of the oil flow passage 33, that is defined by the base plate 27. The base plate 27 is formed with an outlet opening 27 b through which an outlet part of the oil flow passage 33 is communicated with the interior 27 c of the base plate 27. Thus, under the above-mentioned mounted condition, the interior 27 c is communicated with only the smaller bore 24 to which the oil passage 17 is connected.

Although not shown in the drawings, the base plate 27 of the oil cooler 14 is formed at its peripheral portion with openings through which connecting bolts pass to tightly connect the oil cooler 14 to the mounting portion 19 of the transmission housing 22. Of course, a suitable sealing member is tightly put between the base plate 27 and the mounting portion 19 for achieving a hermetical sealing therebetween.

In the following, the construction of each depressed element plate 28 will be described with reference to FIGS. 6 to 9.

As is seen from FIG. 6, each element plate 28 is in the form of a circular dish, which comprises a depressed circular major portion 28 a, an annular flange 29 extending along a periphery of the depressed circular major portion 28 a, two circular simple openings 30 formed in a circular flat base part of the major portion 28 a and two collared circular openings 31 formed also in the flat base part of the major portion 28 a.

As shown, the circular simple openings 30 are arranged at diametrically opposed positions and also the collared circular openings 31 are arranged at diametrically opposed positions. Preferably, these openings 30 and 31 are arranged so that an imaginary line passing through centers of the two simple openings 30 and another imaginary line passing through centers of the two collared openings 31 meet at right angles.

As is seen from FIG. 8, each simple circular opening 30 has a predetermined diameter “φ1”, while, as is seen from FIG. 7, each collared circular opening 31 has a tapered collar portion that has a predetermined length “H”. Furthermore, the collared opening 31 has an annular ridge 32 that forms a leading end of the tapered collar portion. The annular ridge 32 has a predetermined diameter “φ2” that is equal to or slightly larger than the diameter “φ1” of the simple opening 30.

As will be seen from FIG. 9, when, after turning 90 degrees about its center axis, one element plate 28A is put on another element plate 28B and pressed downward, a tapered outer wall of the element plate 28A intimately receives a corresponding outer wall of the element plate 28B and at the same time, the annular ridges 32 of the two collared circular openings 31 of the element plate 28A are thrust into the simple openings 30 of the element plate 28B respectively. With this procedure, a thin passage R is defined between these two element plates 28A and 28B as is seen from the drawing. (Thus, if a third element plate (not shown) is put on the element plate 28A in the above-mentioned manner, another thin passage is defined between the third element plate and the element plate 28A.) Actually, in a subsequent procedure, the contact portion between the respective tapered outer walls of the two element plates 28A and 28B and the contact portion between the annular ridges 32 of the element plate 28A and peripheries of the simple openings 30 of the element plate 28B are brazed to achieve a hermetical sealing therebetween. That is, a brazing technique or the like is applied to such contact portions.

A method of stacking or assembling the nine element plates 28A, 28B, 28C, 28D, . . . 28I will be understood from the following description when taken in conjunction with FIG. 10.

That is, as is understood from the drawing, before stacking them together, every neighboring element plates 28A and 28B (or 28B and 28C, 28C and 28D, 28D and 28E, 28E and 28F, 28F and 28G, 28G and 28H or 28H and 28I) are angled by 90 degrees about their common axis.

Then, the uppermost and lowermost element plates 28A and 28I are pressed toward each other.

With this press work, there are produced or defined both the water flow passage 34 and the oil flow passage 33. That is, the water flow passage 34 includes the simple openings 30A, a thin circular passage defined between the element plates 28A and 28B, passages defined by the collared openings 31B and the simple openings 30C, a thin circular passage defined between the element plates 28C and 28D, passages defined by the collared openings 31D and the simple openings 30E, a thin circular passage defined between the element plates 28E and 28F, passages defined by the collard openings 31F and the simple openings 30G and a thin circular passage defined between the element plates 28H and 28I. The oil flow passage 33 includes passages defined by the collared openings 31A and the simple openings 30B, a thin circular passage defined between the element plates 28B and 28C, passages defied by the collared openings 31C and the simple openings 30D, a thin circular passage defined between the element plates 28D and 28E, passages defined by the collared openings 31E and the simple openings 30F, a thin circular passage defined between the element plates 28F and 28G, passages defined by the collared openings 31G and the simple openings 30H and a thin circular passage defined between the element plates 28H and 28I.

As has been mentioned hereinabove, once the nine element plates 28A to 28I are properly stacked or assembled together in the above-mentioned manner, the unit of them is subjected to a brazing process for achieving a hermetical sealing of mutually contacting portions of the element plates. Thus, the water flow passage 34 and the oil flow passage 33 are isolated from each other.

Operation of the oil cooling and filtering system of the present invention will be described with reference to FIGS. 1, 2, 4 and 5.

As is seen from FIGS. 1 and 4, under operation of the automatic transmission, cooling water from the radiator is led into the water flow passage 34 of the oil cooler 14 through the water inlet pipe 14 a and returned back to the radiator through the water outlet pipe 14 c, and at the same time, the lubricating oil from the control valve 12 is led into the oil filter 20 and then led into the oil flow passage 33 of the oil cooler 14 and directed toward the moving parts 13 of the transmission through the smaller bore 24 and the oil passage 17.

During this flow, the lubricating oil is filtered by the oil filter 20 and then cooled by the oil cooler 14, and thus, the lubricating oil actually applied to the moving parts 13 of the transmission can exhibit a satisfied lubricating performance to the moving parts 13.

Although the foregoing description is directed to the embodiment wherein the oil filter 20 is installed in the oil passage 16 that is positioned upstream of the oil cooler 14, the oil filter 20 may be installed in the oil passage 17 that is positioned downstream of the oil cooler 14. In this case, any foreign things that would appear in the oil cooler 14 can be instantly removed by the oil filter 20 before being led to the moving parts 13.

As is understood from the foregoing description in accordance with the present invention, since the oil filter 20 is set in the transmission housing, not in the oil cooler 14, the oil cooler 14 can be compact in size and simple in construction without being obstructed by the oil filter 20. This is quite advantageous when considering the difficulty with which various parts have to be mounted in an engine room that has a limited space. Furthermore, simple construction of the oil cooler 14 brings about a reduction in cost of the oil cooling and filtering system of the transmission.

The entire contents of Japanese Patent Application 2004-103978 filed Mar. 31, 2004 are incorporated herein by reference.

Although the invention has been described above with reference to the embodiment of the invention, the invention is not limited to such embodiment as described above. Various modifications and variations of such embodiment may be carried out by those skilled in the art, in light of the above description. 

1. An oil cooling and filtering system of a transmission, comprising: first and second oil passages formed in a given portion of a housing of the transmission, the given portion having an outer surface exposed to the outside of the housing, the first oil passage being fed with a compressed lubricating oil from an oil compressing means and the second oil passage being led to moving parts of the transmission which are to be lubricated; an oil cooler connected to the outer surface of the given portion, the oil cooler including a water flow passage and an oil flow passage which are isolated from each other, the oil flow passage having an inlet opening connected to the first oil passage and an outlet opening connected to the second oil passage; and an oil filter installed in at least one of the first and second oil passages for filtering the lubricating oil flowing in the oil passage.
 2. An oil cooling and filtering system as claimed in claim 1, in which the oil filter is installed in the first oil passage for filtering the lubricating oil flowing in the first oil passage toward the oil cooler.
 3. An oil cooling and filtering system as claimed in claim 2, in which the first oil passage is formed with an enlarged portion in which the oil filter is installed.
 4. An oil cooling and filtering system as claimed in claim 3, in which the enlarged portion of the first oil passage is formed in the given portion in such a manner that the enlarged portion terminates at the outer surface of the given portion of the transmission housing.
 5. An oil cooling and filtering system as claimed in claim 4, in which the enlarged portion of the first oil passage is formed with a filter seat portion on which an end of the oil filter is seated.
 6. An oil cooling and filtering system as claimed in claim 5, further comprising a seal member which is put between the filter seat portion and the end of the oil filter.
 7. An oil cooling and filtering system as claimed in claim 3, in which the enlarged portion of the first oil passage is a cylindrical bore and the oil filter is cylindrical in shape.
 8. An oil cooling and filtering system as claimed in claim 7, in which a diameter of the cylindrical oil filter is smaller than a diameter of the cylindrical bore.
 9. An oil cooling and filtering system as claimed in claim 1, in which the oil cooler comprises: a circular depressed base plate; a circular cover plate; and a plurality of circular depressed element plates which are the same in shape, the circulate depressed element plates being stacked together between the circular depressed base plate and the circular cover plate in such a manner as to form the water flow passage and the oil flow passage.
 10. An oil cooling and filtering system as claimed in claim 9, in which each of the circular depressed element plates comprises: a depressed circular major portion; an annular flange extending along a periphery of the depressed circular major portion; two circular simple openings formed in a circular flat base part of the depressed circular major portion; and two collared circular openings formed also in the circular flat base part of the depressed circular major portion, wherein every neighboring two of the stacked circular depressed element plates are so arranged that the collared openings of one circular depressed element plate are mated with the simple openings of the other circular depressed element plate thereby to define between the two circular depressed element plates a thin space that forms part of either one of the water flow passage and the oil flow passage.
 11. An oil cooling and filtering system as claimed in claim 10, in which the two circular simple openings are located at diametrically opposed positions of the circular flat base part of the depressed circular major portion, and in which the two collared openings are located at diametrically opposed positions of the circular flat base part of the depressed circular major portion.
 12. An oil cooling and filtering system as claimed in claim 11, in which the two circular simple openings and the two collared circular openings are arranged so that an imaginary line passing through centers of the two circular simple openings and another imaginary line passing through centers of the two collared circular openings meet at right angles.
 13. An oil cooling and filtering system of an automatic transmission comprising: first and second oil passages formed in a given portion of a housing of the transmission, the given portion having a flat outer surface exposed to the outside of the housing, the first oil passage terminating at the flat outer surface and being fed with a compressed lubricating oil from an oil pump, the second oil passage terminating at the flat outer surface and being led to moving parts of the transmission which are to be lubricated; an oil cooler detachably connected to the flat outer surface of the given portion, the oil cooler including a water flow passage and an oil flow passage which are isolated from each other, the oil flow passage having an inlet opening connected to the first oil passage and an outlet opening connected to the second oil passage; a cylindrical bore formed in the given portion of the housing and merged with the first oil passage, the cylindrical bore terminating at the flat outer surface of the given portion; and a cylindrical oil filter installed in the cylindrical bore of the given portion for filtering the lubricating oil flowing in the first oil passage toward the oil cooler. 